The present invention relates to an image reproducing method to reproduce an image of an object on a print, an image reproducing system and an image processing apparatus.
As a theoretical reproduction of gradation, it has been known to determine density of a reproduced image so that the sum of a logarithm of object brightness and density of the reproduced image may be constant. This method, however, has been considered to have a problem that gradation of an image of an object with high luminance can not be reproduced, because density on a print can not be zero or less, Therefore, it has generally been conducted in the photographic industry that gradation of an object image on the part of high luminance is barely reproduced by reproducing a low density area of a reproduced image on a print (an area of the density covering from the lowest density to the density representing the lowest density plus 0.5) to be soft in terms of gradation.
In the case of a color print, in particular, colors and signals of an image pickup medium for each primary color have color cross-over, and color dyes forming a color print are not pure primary colors. For making color reproduction in the vicinity of luminance of a primary object to be excellent, therefore, it has generally been conducted in the photographic industry that a density area excluding a low density area of the reproduced image on a print is reproduced to be high in terms of contrast.
Further, since a range of colors reproducible on a print is considerably smaller than that of actual object brightness, it is conducted in the electrical machinery industry that colors are compressed with various color coordinate systems such as CIELUV and CIELAB to be reproduced.
In the method generally used in the photographic industry, however, even when a primary object such as a person is photographed with frontal lighting under a blue sky, for example, the sky is reproduced to be light gray on a color print, making the color print look as if it was photographed under a clouded sky, because an image of an object on the part of high luminance is reproduced to be soft in terms of gradation.
With regard to a face of a person representing an important object, when the face is of a bright flesh color, it is preferable that the face is reproduced to be bright on a print. In the method used generally in the photographic industry, however, sufficient gradation feeling can not be obtained, resulting in an image lacking three-dimensional feeling, because an image of an object reproduced on the part of low density on a print, mamely, an image of an object on the part of high luminance is reproduced to be soft in terms of gradation. In addition, in the same way as in the foregoing, when an image of an object with bright color is reproduced to be bright, sufficient gradation feeling can not be obtained, resulting in an image lacking three-dimensional feeling.
Further, when a density area excluding a low density area of a reproduced image on a print is made to be high in terms of contrast, a density area where gradation can be reproduced sufficiently is narrowed, which is a problem. In the case of a color print, there sometimes occurs undesirable color reproduction such as an occasion where a color of a face with a bright flesh color tends to be reproduced to be more yellowish than its actual color.
A method to reproduce through color compression conducted with various color coordinate systems such as CIELUV and CIELAB requires complicated operations to convert color image information into color coordinates systems in an even color space such as CIELUV and CIELAB, further, to conduct color compression processing with the color coordinates systems in an even color space, and thereby to convert from the color coordinates systems in an even color space to information of color images in blue, green, red or yellow, magenta and cyan (, black), and yet the reproduction made by the method is still inferior to that made by a conventional method in the photographic industry.